1. Field of the Invention
The invention relates to a material return system of a material collection system that uses the venturi effect to flush fine material back into a collection vessel.
2. Description of the Related Art
Various systems have been designed to collect bulk materials into a storage receptacle using a vacuum. Most bulk materials comprise a wide range of particle sizes from large/coarse to fine. One of the known problems is that when collecting material having this wide range of particle sizes, it is difficult to contain the fine material because of its tendency to be disturbed and blown around by the forces on the air exerted by the vacuum. These fine materials can, over time, collect in undesirable locations and prevent proper operation of the system
The traditional way of returning the fine materials or carry over from the process of vacuuming dense bulk materials into a vacuum collection vessel or debris tank is to use mechanical devices such as augers, conveyers or other mechanisms to hold the fine material in a collection chamber, bag house or dump tubes that have to be mechanically empted/dumped when the debris tank is full. Vacuum sealing of augers, conveyers and dump tubes are high maintenance items. Since the tubes can only be dumped after the material is transported to a dump site, the material settles and packs during transport and requires vibrators or manual cleaning to clean out the tubes or bag houses. In order to prevent an accumulation of this fine material that would preclude operation of the system, frequent inefficient stops may be needed to empty the fine material.
U.S. Pat. No. 4,227,893 discloses an auger used for mechanically returning fine materials to the bulk collection portion of the debris tank, however the auger represents a mechanical apparatus that increases the system complexity and introduces costs to the system.
U.S. Pat. No. 4,017,281 discloses a material collection system in which the fine material is collected from a dust collecting chamber by a pipe connected to a door/port and relies exclusively on a pressure differential between the dust collection chamber and the hopper to remove the fine material. Since the pressure differential is of concern for performing an effective job, this differential must be maximized in order to maximize the cleanout of the dust collecting chamber. This results in a nonoptimized solution.